Primordial Mars Resembled Primordial Earth

The layering of minerals in an ancient Martian riverbed channel suggests that primordial Mars resembled primordial Earth, and may have been just as suitable for life.

The analysis, based on data returned by the Mars Reconnaisance Orbiter and published today in Science, is perhaps the most exciting in a string of recent red planet findings.

"The environment was probably habitable as we define it," said Jim Bell, a specialist in Martian geology who was not involved in the study. "If there were any life forms, they would have been in an environment conducive to their survival, even their thriving."

In June, stunning time-lapse images of evaporating ice verified the long-suspected presence of Martian water. Scientists soon reported that Martian water was once widespread, playing a central role in the planet’s development. Earlier this week, NASA announced the discovery of perchlorate, a molecule metabolized by some Earthly bacteria.

Today’s study describes Mawrth Vallis, a channel cut 3.5 billion years ago by water flowing through the Noachian highlands of Mars’ southern hemisphere. Geologists found extensive deposits of a type of iron that — at least on Earth — is formed by the weathering of volcanic rocks by water, and is known for supporting bacterial life.

"On Earth, if this type of iron is around, then bacteria use it," said said study co-author John Mustard, a Brown University geologist.

Even more tantalizing, Mustard’s team found layers of clay minerals likely formed by the long-term leaching of water through the iron. "The geometric relationships," said Mustard, "imply a lot of water. Rainfall." That, said Bell, implies higher temperatures that could only be provided by an atmosphere.

"Mars was much more Earth-like than it is today," said Bell. "We don’t know if it was a living planet, but there would have been lakes, ponds, rivers, snowfall and glaciers."

Both researchers cautioned that the layering could be a geological coincidence, but favored water as the explanation. And with water, warmth and basic minerals provided, the last piece needed for life as we know it is carbon-bearing organic molecules. Those could easily have been deposited by meteors that peppered Mars during its infancy, said
Mustard.

The key question now, said Bell, is whether these conditions existed long enough to support life’s emergence.

"If it was a flash in the pan, it may not have been enough time for complex chemistry and the formation of life and evolution to appear,"
he said. "But if it was a billion years, or just many hundreds of millions, you get into the same situation we believe early Earth was in. And once the environment formed on early Earth, life followed quickly."